A motley prehistoric crew get animated in the hilarious CG smash that introduced us to Sid the Sloth, Manfred the Mammoth, Scrat the acorn-obsessed whatever-he-is, and a whole host of other colourful characters trying to cope with the oncoming ice age. "They came. They thawed. They conquered" went the tagline - and so they did, with three hit sequels to prove it.
With its first full-length, digitally animated film, 20th Century Fox commences battle with Disney and Dreamworks.
It's a tall order...but the result is an enchanting tale where the film-makers have wisely devoted as much effort into characterisation as the very splendid computer animation.
The ice age - think a global cold snap that lasts thousands of years - is beginning and a mass movement of pre-historic animals, plus an early tribe of humans, are moving south.
However, one human has seriously cheesed off a bunch of sabre-toothed tigers, one of whom - Diego - (voiced by Denis Leary) is sent to snatch the man's child.
Enter woolly mammoth (Ray Romano) and his unwanted companion, a constantly chattering sloth (John Leguizamo).
This unusual pair, coming across the abandoned baby, determine to protect it from the tiger and return it to its tribe.
Rich characterisation and superb visuals distinguish this computer-generated debut from Fox's Blue Sky Studios, a film-making team who cut their teeth on the groundbreaking Disney sci-fi outing Tron.